习题 7-2 uva225（回溯）

#include <iostream>
#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <queue>
#include <algorithm>
typedef long long ll;
using namespace std;
const int inf = 0x3f3f3f3f;
int tx[100];
int ty[100];
int dir[4][2] = {{1,0},{0,1},{0,-1},{-1,0}};
int vis[1000][1000];
char dire[] = {"ensw"};
int all;
struct node
{
int step;
int x,y;
int dir;
};
int n,k;
int ans[200];

bool judge(int i,node a)    //判断是否能走
{
int x = a.x+dir[i][0]*(a.step+1);
int y = a.y+dir[i][1]*(a.step+1);
if(i == 1 || i == 2)
{
for(int j = 0; j < k; j++)
{
if(tx[j] == x && ty[j] >= y && ty[j] <= a.y && i == 2)
return true;
if(tx[j] == x && ty[j] >= a.y && ty[j] <= y && i == 1)
return true;
}
}
if(i == 0 || i == 3)
{
for(int j = 0; j < k; j++)
{
if(ty[j] == y && tx[j] >= x && tx[j] <= a.x && i == 3)
return true;
if(ty[j] == y && tx[j] >= a.x && tx[j] <= x && i == 0)
return true;
}
}
return false;
}

void dfs(node a)
{
if(a.x == 220 && a.y == 220 && a.step == n)
{
//        printf("%d\n",a.step);
//        for(int i = 0; i < a.step;i++)
//            printf("%d ",ans[i]);
//        printf("\n");
for(int i = 0; i < a.step; i++)
{
printf("%c",dire[ans[i]]);
}
printf("\n");
all++;
return ;
}
if(a.step >= n)
return;

for(int i = 0; i < 4; i++)
{
if(i == 0 && (a.dir == 3||a.dir == 0))continue;
if(i == 1 && (a.dir == 2||a.dir == 1))continue;
if(i == 2 && (a.dir == 1||a.dir == 2))continue;
if(i == 3 && (a.dir == 0||a.dir == 3))continue;

if(judge(i,a))
continue;
node tt = a;
ans[a.step] = i;
tt.x = a.x+dir[i][0]*(a.step+1);
tt.y = a.y+dir[i][1]*(a.step+1);
if(vis[tt.x][tt.y])
continue;
vis[tt.x][tt.y] = 1;
tt.dir = i;
tt.step = a.step + 1;
dfs(tt);
vis[tt.x][tt.y] = 0;
}
return ;
}

int main()
{
int cas = 1,T;
int a,b;
scanf("%d ",&T);
while(T--)
{
scanf("%d %d ",&n,&k);
memset(vis,0,sizeof(vis));
for(int i = 0; i < k; i++)
{
scanf("%d %d",&a,&b);
tx[i] = a+220;
ty[i] = b+220;
}
node cur;
all = 0;
cur.x = 220,cur.y = 220,cur.step = 0,cur.dir = -1;
dfs(cur);
printf("Found %d golygon(s).\n",all);
printf("\n");
}
return 0;
}